Fatigue is a significant problem in people with diabetes (DM), the consequences of which can undermine the ability to engage in diabetes self-management behaviors. Exercise participation may be especially vulnerable to the effects of fatigue. Surprisingly, there is only limited research related to fatigue in diabetes, leaving a significant gap in the knowledge. In order to better understand diabetes fatigue and its consequences, a cross-sectional study of individuals with type 1 and type 2 DM will be undertaken. A proposed model of the physiological, psychological, and behavioral correlates of fatigue will be used as an organizing framework. The aims of the proposal are to (a) describe the impact of physiological and psychological correlates of fatigue in individuals with DM, (b) explore differences in experiences between individuals with type 1 and type 2 DM, and (c) describe the interrelationship between fatigue, exercise behavior, and exercise capacity. Descriptive correlation and regression analyses will be used. Findings will help to understand the role fatigue plays in exercise behaviors and capacity, and ultimately provide a framework for interventions aimed at increasing physical activity among people with diabetes.